American Medievalist of Spanish architecture and Americanist; Librarian and Director of the Boston Athenaeum.
Whitehill's parents were Walter Muir Whitehill, an Episcopal minister, and Florence Marion Williams (Whitehill). He entered Harvard University, receiving his A.B. in 1926, and continuing for his A.M., awarded in 1929. Whitehill married Jane Revere Coolidge, a descendant of Thomas Jefferson, in 1930, leaving for Europe the same year to continue his studies. He wrote his dissertation under the eminent American Romanesque scholar A. Kingsley Porter (q.v.) at the University of London, receiving his Ph.D. in 1934. He remained in Europe until 1936, immersed in Spanish architectural history research in Spain. He
returned to the United States in 1936 to become assistant director of the Peabody Museum of Salem, Salem, MA. In 1941 Whitehill published a revised version of his dissertation, Spanish Romanesque Architecture of the Eleventh Century, founding the American Neptune: A Quarterly Journal of Maritime History. By this time Whitehill switched interests to American art.
During World War II, Whitehill served in the Naval Reserve, assigned to active duty from 1942-1946 and discharged with the rank of commander. After the war, he joined the Boston Athenaeum, the private library, as director and librarian in 1946, which he held until his retirement in 1973. Whitehill was appointed a member of faculty of Harvard University associated with the Peabody Museum of Archaeology and Ethnology in 1951 and a lecturer in history for the 1956-1957 year. Whitehill became a champion of architectural preservation in Boston. In 1961 he succeeded in saving the Old Corner Bookstore. Whitehill maintained a country house in Starksboro, VT, where he and his wife entertained in a gentlemanly manner.
He became a Trustee of Museum of Fine Arts, Boston. In 1965 he published a survey, The Arts in Early American History. A two-volume centenary history of the Museum of Fine Arts, Boston, appeared in 1970. Whitehill retired from the Athenaeum in 1973, publishing his Boston Prints and Printmakers the same year. In retirement, he issued an architectural work, Palladio in America. One of his final acts was helping to preserve the Quincy Market area in Boston in 1976. He suffered a stroke and died at age 72. He is buried on the grounds of Monticello, Jefferson's home, in accordance to Jefferson's will regarding Jefferson's descendents. His papers are held at the Massachusetts Historical Society.

Though Whitehill's publishing career focused on Bostoniana, his work on Spanish medieval art represents the earliest American interest in the subject. He, Porter, Georgiana Goddard King (q.v.), Walter W. S. Cook (q.v.), Kenneth John Conant (q.v.) [the Cluny scholar's dissertation on the cathedral of Santiago de Compostela) and Chandler Rafton Post (q.v.) formed something of a "New England School" in Spanish art (Cahn).